The instant invention relates to welding apparatus and more particularly to welding apparatus for use in conjunction with automatic link forming apparatus.
In making jewelry, it is conventional to attach ornaments or findings to a chain by taking a small diameter U-shaped wire, placing a ring attached to the ornament over the free ends of the wire and forming the wire into a closed link. The closed ends of the wire are then permanently joined by either soldering or welding to prevent them from separating.
Heretofore, there have been known in the art link forming apparatus which are operable for automatically forming the U-shaped wire workpieces, presenting them for attachment to a chain or finding and closing the open ends of the wire around the chain or finding. One such machine is disclosed in the U.S. Pat. No. to Crafford, et al, 3,841,088. This apparatus forms the U-shaped workpieces from a continuous length of wire stock and feeds the workpieces to a workpiece holder for holding of the bight of the U-shaped workpiece. A chain or other finding is manually placed over the free ends of the workpiece and a camming head is then actuated into engagement with the free ends of the wire bending the ends into a closed loop or link. The link is then ejected from the holder and another workpiece is presented for attachment and closure. The ejected link can then be soldered or welded in a separate operation.
There have also been known in the art welding apparatus which operate in conjunction with the conventional link forming apparatus to automatically weld the ends of the link after closure thereof. Such apparatus is disclosed in the U.S. Pat. No. to Brastow, et al, 4,388,513. This apparatus positions a movable welding head adjacent to the link forming apparatus and it is adapted to move the electrode thereof to and from the workpiece holder via a linkage assembly which is actuated by a solenoid. A complete cycle for forming and welding a link comprises the following steps: presenting the workpiece for closure, actuating the camming head to descend and bend the free ends of the workpiece into a closed link, retracting the camming head, actuating the electrode of the welding head to the workpiece and positioning it a selected distance therefrom, moving a shield into position in front of the workpiece and ionizing the air around the workpiece by directing a selected gas around the workpiece. Once the proper ionization level is reached a welding arc travels from the electrode to the workpiece to effect the weld. The electrode is then retracted, the shield removed and the workpiece is released and a new workpiece is presented at the workpiece holder.
Although the device disclosed in the Brastow patent is effective for automatically forming the welds, there are several disadvantages which will become apparent. It is pointed out that the electrode head of the Brastow device is presented from the rear of the workpiece holder. Rear presentation often interferes with larger and odd shaped finding or ornaments which must be positioned adjacent the workpiece holder for attachment to the link. It has been found that the large findings often block the forward travel of the electrode head thereby preventing the welding operation. Rear presentation of the electrode head also prevents welding of odd shaped wire stock, such as half-round stock and flat stock. Because of the shape of the stock, an electrode which is presented from the rear of the workpiece holder must weld through the thickest dimension of the wire. Welding through the thickest dimension of the wire requires increased electrical discharge. It has been found that the increased electrical discharge often disfigures or disintegrates the rearward portions of the link before the weld can travel through to the forward portions of the link. The inability to weld half-round and flat stock is a significant disadvantage in the current marketplace because use of these types of linking materials is becoming more and more popular.